1. School of Biology, Centre for Social Learning and Cognitive Evolution; University of St. Andrews; Queen's Terrace, St. Andrews Fife KY16 9TS U.K.
2. Department of Anthropology; Centre for Coevolution of Biology & Culture, Durham University; Dawson Building, Mount Joy Site Durham DH1 3LE U.K.
3. Department of Psychology; Centre for Coevolution of Biology & Culture, Durham University; Mount Joy Site Durham DH1 3LE U.K.